The present invention relates to a rotary hammer drill for undercutting a hole for an anchor bolt in hardened concrete.
Conventionally, an anchor bolt has been set in hardened concrete by cutting a cylindrical blind hole in the concrete using a hammer drill or the like, inserting the bolt into the hole, and then expanding a split skirt or sleeve of the bolt into frictional engagement with the wall of the cylindrical hole. Recently drills have also been produced which form an undercut or cavity below the surface of the concrete, and anchor bolts which can be expanded into the cavity.
It is a general object of this invention to provide an improved drill for forming an undercut conical or annular cavity in the cylindrical wall of a hole drilled in concrete, whereby an expanded skirt of an anchor bolt extends into and engages the cavity so as to securely hold the bolt in the hole.